In a variety of machines, such as engine-powered vehicles, instruments are employed to detect the presence of various undesirable operating conditions, such as overheating of the engine, sensor failure, low oil pressure, low fuel, and the like, and indicators are provided to warn the operator of such conditions. For example, these instruments may include monitoring systems, diagnostic systems, or control systems and are often designed to operate in connection with a variety of machine types.
These instruments are typically connected to various sensors and switches for monitoring or controlling conditions on the vehicle via a wire harness and/or a communication link. In many applications, these instruments are also connected to electronic control systems such as electronic engine controls, electronic transmission controls, and the like.
Since these instruments may be used in connection with many different machines, it is advantageous for the instruments to be as flexible as possible. Lower costs are achieved and less warehousing space are required if a single instrument is manufactured which can be used in many different applications. Similarly, service time is reduced if software changes are avoided when an instrument is moved from one machine to another or when an electronic control is added to an existing machine as an attachment.
Most prior art systems have included dedicated instruments in which the functions and conditions of the vehicle to be monitored or diagnosed, as well as the particular sensors provided on the vehicle are identified in advance. Hence, the instrument is specifically designed for and hence "dedicated" to the monitoring of those particular vehicle functions and conditions in response to signals from the particular, pre-identified associated sensors. Accordingly, such "dedicated" instruments generally cannot be readily modified in the field to accommodate different machines, different sensors and/or different conditions and functions. Rather, such instruments are generally limited to use with a particular machine type or a particular group of attachments for which the instrument has been designed.
However, a manufacturer of monitoring or diagnostic equipment need not provide a totally new monitoring system for each vehicle or each variation in vehicle sensors or functions to be monitored. While some prior art systems have provided for standardized monitoring systems, for example the system shown in U.S. Pat. No. 4,551,801, this monitoring system is still relatively inflexible and requires the addition or subtraction of monitoring modules and the use of decals to indicate the parameters being shown by each display module.
In connection with some machines, parameter data is obtained by the instrument from a sensor wired directly to the instrument, while in connection with other machines data for monitored parameters is obtained from an electronic control via a communication link.
If an instrument is unable to receive data from either source, different instruments must be manufactured for use in connection with each machine type or the software within a computerized instrument must be modified. The instrument display should also be able to be reconfigured while on the vehicle to receive data from a different source with little or no work required from the serviceman.
In some cases, the use of vehicle identification codes to determine which source will deliver data to the instrument may be used, however, vehicle identification codes are insufficient in the event that electronic controls are added as attachments to a vehicle. Identification codes also may not be feasible if the amount of information that may be conveyed by the identification code is limited by harness connector pin availability since each bit of the identification code requires a connector pin.
As an example of an electronic control being added to a machine as an attachment, a machine having a mechanical shifting transmission that is later equipped with an electronic transmission control will have the engine speed sensor wiring rerouted from the instrument display to the electronic transmission control because data delivered to the transmission control must be in real time. Since the instrument is no longer reading the engine speed sensor, the diagnostics for that sensor must be disabled. Also, since the engine speed data will now be read from the communications link, the diagnostics for a loss of signal on the communications link must be enabled.
The present invention is directed to overcoming one or more of the problems set forth above.